Method and apparatus for management of heart failure hospitalization

ABSTRACT

A hospitalization management system including a heart failure analyzer that receives diagnostic data including at least sensor data representative of one or more physiological signals sensed from a hospitalized patient using one or more sensors and assesses risk of rehospitalization for the patient using the diagnostic data. The outcome of the risk assessment is used during and following the patient&#39;s hospitalization for reducing the risk of rehospitalization.

CLAIM OF PRIORITY

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. §120 to U.S. patent application Ser. No. 13/668,659,filed on Nov. 5, 2012, now issued as U.S. Pat. No. 8,708,924, which is acontinuation of and claims the benefit of priority under 35 U.S.C. §120to U.S. patent application Ser. No. 13/279,517, filed on Oct. 24, 2011,now issued as U.S. Pat. No. 8,303,513, which is a continuation of andclaims the benefit of priority under 35 U.S.C. §120 to U.S. patentapplication Ser. No. 11/685,949, filed on Mar. 14, 2007, now issued asU.S. Pat. No. 8,052,611, which is hereby incorporated by referenceherein in its entirety.

TECHNICAL FIELD

This document relates generally to medical device systems andparticularly to a system providing for management of hospitalization ofheart failure patients having implantable devices.

BACKGROUND

The heart is the center of a person's circulatory system. It includes anelectro-mechanical system performing two major pumping functions. Theleft side of the heart, including the left atrium and left ventricle,draws oxygenated blood from the lungs and pumps it to various organs ofthe body to provide the organs with oxygen for their metabolic needs.This pumped blood flow is called the cardiac output. The right side ofthe heart, including the right atrium and right ventricle, drawsdeoxygenated blood from the organs and pumps it into the lungs where theblood gets oxygenated. The pumping functions are accomplished bycontractions of the myocardium (heart muscles). In a normal heart, thesinoatrial node, the heart's natural pacemaker, generates electricalimpulses, known as action potentials, that propagate through anelectrical conduction system to various regions of the heart to excitemyocardial tissues in these regions. Coordinated delays in thepropagations of the action potentials in a normal electrical conductionsystem cause the various regions of the heart to contract in synchronysuch that the pumping functions are performed efficiently.

A blocked or otherwise damaged electrical conduction system causesirregular contractions of the myocardium, a condition generally known asarrhythmia. Arrhythmia reduces the heart's pumping efficiency and hence,diminishes the cardiac output. The diminished cardiac output may also becaused by heart failure where the myocardial muscle is weakened and itscontractility is reduced. A heart failure patient usually suffers fromboth a damaged electrical conduction system and a deterioratedmyocardium. In response to the reduced cardiac output, the body attemptsto adapt in a number of ways that lead to various symptoms as the heartfailure condition progresses. The body retains salt and water as aresult of reduced urinal output. The salt and water are then accumulatedin the lung and/or in peripheral tissues. The water retention may alsolead to acute pulmonary edema in which fluid leaks into the air sacs ofthe lung, causing the patient to gasp for breath. This condition can befatal if not treated immediately. Another symptom of a patient withheart failure is fatigue on exertion. Once diagnosed with chronic heartfailure, the patients is typically managed by interventions such as dietrestriction and pharmacologic and/or device therapies. Suchinterventions keep the patient in a clinically stable state unlesspunctuated by episodes of acute heart failure decompensation. Acuteheart failure decompensation is characterized by fluid overload andshortness of breath, and requires immediate treatment in a hospital oran outpatient clinical setting.

Heart failure has been recognized as a significant public health concernwith a huge economic impact. Patients hospitalized with decompensatedheart failure reportedly have a high rate of rehospitalization withinsix months (more than 50% according to some studies), with a significantpercentage of them rehospitalized within a month. Hospital readmissionis a principal factor responsible for the cost associated with managingheart failure. Premature hospital discharge and insufficient resolutionof heart failure worsening are among the factors contributing to thehigh rate of rehospitalization. Therefore, there is a need to improvemanagement of heart failure hospitalization for reducing the rate ofrehospitalization.

SUMMARY

A hospitalization management system including a heart failure analyzerthat receives diagnostic data including at least sensor datarepresentative of one or more physiological signals sensed from ahospitalized patient using one or more sensors and assesses risk ofrehospitalization for the patient using the diagnostic data. The outcomeof the risk assessment is used during and following the patient'shospitalization for reducing the risk of rehospitalization.

In one embodiment, a hospitalization management system includes one ormore sensors, a sensor processing circuit, and a heart failure analyzer.The one or more sensors sense one or more physiological signals. Thesensor processing circuit produces sensor data representative of thesensed one or more physiological signals. The heart failure analyzerincludes a data input, a diagnostic data processor, a mode switch, and arisk analyzer. The data input receives diagnostic data indicative of oneor more conditions associated with heart failure. The data inputincludes a sensor data input to receive the sensor data. The diagnosticdata processor produces one or more parameters using the diagnosticdata. The mode switch switches an operational mode of the heart failureanalyzer to a hospitalization mode in response to a mode-change command.The risk analyzer produces a risk class parameter during thehospitalization mode. The risk class parameter classifies a level ofrisk for rehospitalization within a specified period using the one ormore parameters.

In one embodiment, a method for operating a heart failure analyzer formanaging hospitalization of a heart failure patient is provided. One ormore physiological signals are sensed. Sensor data representative of thesensed one or more physiological signals are produced. Diagnostic dataindicative of one or more conditions associated with heart failure,including the sensor data, are received. One or more parameters areproduced using the diagnostic data. An operational mode of the heartfailure analyzer is switched to a hospitalization mode in response to amode-change command. A risk class parameter is produced using the one ormore parameters during the hospitalization mode. The risk classparameter classifies a level of risk for rehospitalization.

This Summary is an overview of some of the teachings of the presentapplication and not intended to be an exclusive or exhaustive therapy ofthe present subject matter. Further details about the present subjectmatter are found in the detailed description and appended claims. Otheraspects of the invention will be apparent to persons skilled in the artupon reading and understanding the following detailed description andviewing the drawings that form a part thereof. The scope of the presentinvention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate generally, by way of example, variousembodiments discussed in the present document. The drawings are forillustrative purposes only and may not be to scale.

FIG. 1 is an illustration of an embodiment of a hospitalizationmanagement system and portions of the environment in which thehospitalization management system operates.

FIG. 2 is a block diagram illustrating an embodiment of portions of acircuit of the hospitalization management system.

FIG. 3 is a block diagram illustrating an embodiment of a heart failureanalyzer of the hospitalization management system.

FIG. 4 is a graph illustrating an example of a parameter indicative ofprogression of heart failure.

FIG. 5 is a block diagram illustrating an embodiment of a heart failuremanagement module of the heart failure analyzer.

FIG. 6 is a flow chart illustrating a method for managinghospitalization of a heart failure patient.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description provides examples, and thescope of the present invention is defined by the appended claims andtheir legal equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. In this document, the term“or” is used to refer to a nonexclusive or, unless otherwise indicated.Furthermore, all publications, patents, and patent documents referred toin this document are incorporated by reference herein in their entirety,as though individually incorporated by reference. In the event ofinconsistent usages between this documents and those documents soincorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

It should be noted that references to “an”, “one”, or “various”embodiments in this document are not necessarily to the same embodiment,and such references contemplate more than one embodiment.

This document discusses a hospitalization management system thatprovides for management of heart failure patient including riskstratification using data acquired by a medical device implanted in thepatient. Efforts have been to reduce the rate of hospitalization by, forexample, assessing the risk of rehospitalization for a hospitalizedpatient by analyzing the patient's medical history and measurements madeduring hospitalization. Hospital discharge is planned based on theoutcome of the risk assessment. Following the discharge, the patient ismonitored for need of medical attention when certain symptoms occur. Thepresent system automates such practice to allow them to be performed ina timely and consistent manner while the heart failure patient is in thehospital and following the patient's discharge from the hospital,thereby reducing the risk of rehospitalization and improving thepatient's quality of life. In various embodiments, the present systemanalyzes physiological data acquired using one or more sensors implantedin the patient for therapy monitoring, risk stratification, anddischarge planning during the hospitalization and for monitoring andintervention after the hospitalization. In one embodiment, the one ormore sensors are part of an implantable CRM system implanted in thepatient. The implantable CRM system communicates with an externalpatient management system that allows a physician or other caregiver tomonitor, treat, and give instruction to the patient from a remotelocation.

In this document, “hospitalization” includes in-patient hospitalizationand out-patient and clinical care. “Heart failure hospitalization”includes any hospital or clinical setting providing professional carefor a heart failure patient, particularly when acute heart failuredecompensation occurs.

FIG. 1 is an illustration of an embodiment of a hospitalizationmanagement system 100 and portions of the environment in whichhospitalization management system 100 is used. Hospitalizationmanagement system 100 includes an implantable system 105, an externalsystem 125, and a telemetry link 115 providing for bidirectionalcommunication between implantable system 105 and external system 125.Implantable system 105 includes an implantable medical device 110 and alead system 108. Implantable medical device 110 is implanted within abody 102 and coupled to a heart 101 via lead system 108. Examples ofimplantable medical device 110 include, but are not limited to,pacemakers, pacemaker/defibrillators, cardiac resynchronization therapy(CRT) devices, cardiac remodeling control therapy (RCT) devices, andcardiac monitors. In one embodiment, lead system 108 includes multipleatrial and ventricular leads each including one or more electrodes forpacing and/or cardioversion/defibrillation. In one embodiment, externalsystem 125 includes a programmer. In another embodiment, as illustratedin FIG. 1, external system 125 is a patient management system includingan external device 120 in proximity of implantable medical device 110, aremote device 124 in a location relatively distant from implantablemedical device, and a telecommunication network 122 linking externaldevice 120 and remote device 124. The patient management system allowsaccess to implantable system 105 from a remote location, for purposessuch as monitoring patient status and adjusting therapies. In oneembodiment, telemetry link 115 is an inductive telemetry link. Inanother embodiment, telemetry link 115 is a far-field radio-frequency(RF) telemetry link. Telemetry link 115 provides for data transmissionfrom implantable medical device 110 to external system 125. This mayinclude, for example, transmitting real-time physiological data acquiredby implantable medical device 110, extracting physiological dataacquired by and stored in implantable medical device 110, extractingpatient history data such as data indicative of occurrences ofarrhythmias, occurrences of decompensation, and therapy deliveriesrecorded in implantable medical device 110, and extracting dataindicating an operational status of implantable medical device 110(e.g., battery status and lead impedance). Telemetry link 115 alsoprovides for data transmission from external system 125 to implantablemedical device 110. This may include, for example, programmingimplantable medical device 110 to acquire physiological data,programming implantable medical device 110 to perform at least one selfdiagnostic test (such as for a device operational status), programmingimplantable medical device 110 to deliver at least one therapy, andinstructing implantable medical device 110 to analyzing data associatedwith heart failure.

Hospitalization management system 100 includes a heart failure analyzer160 providing for hospitalization management of a heart failure patientusing at least diagnostic data acquired by implantable system 105. Heartfailure analyzer 160 analyzes the diagnostic data for therapymonitoring, risk stratification, and discharge planning duringhospitalization of a heart failure patient and for monitoring andintervention after the hospitalization of the patient. In theillustrated embodiment, heart failure analyzer 160 is substantiallyincluded in implantable medical device 110. In another embodiment, heartfailure analyzer 160 is substantially included in external system 125.In various embodiments, heart failure analyzer 160 is distributed inboth implantable system 105 and external system 125. Heart failureanalyzer 160 may be implemented using a combination of hardware andsoftware. In various embodiments, each element of heart failure analyzer160, including its specific embodiments, may be implemented using anapplication-specific circuit constructed to perform one or moreparticular functions or a general-purpose circuit programmed to performsuch function(s). Such a general-purpose circuit includes, but is notlimited to, a microprocessor or a portion thereof, a microcontroller orportions thereof and a programmable logic circuit or a portion thereof.For example, a “timer” includes, among other things, an electroniccircuit timer constructed to perform the only function of tracking timeor a portion of a general-purpose circuit driven by a code instructingthat portion of the general-purpose circuit to track time.

FIG. 2 is a block diagram illustrating an embodiment of portions of acircuit of hospitalization management system 100, which includes animplantable medical device 210 and external system 225. Implantablemedical device 210 represents an embodiment of implantable medicaldevice 110 and includes one or more sensors 230, a sensor processingcircuit 232, a therapy circuit 234, an implant control circuit 236, animplant memory circuit 238, and an implant telemetry circuit 240.Sensor(s) 230 sense one or more physiological signals. Examples ofsensor(s) 230 include a sensing circuit that senses one or moreelectrograms, a heart sound sensor (such as an accelerometer or amicrophone) that senses a heart sound signal, an impedance sensor thatsenses a transthoracic impedance, a pressure sensor that senses a bloodpressure, such as a pulmonary artery pressure (PAP) sensor that senses aPAP, and a chemical sensor that senses, for example, a blood potassiumlevel. Sensor processing circuit 232 produces sensor data representativeof the sensed one or more physiological signals. Implant memory circuit238 includes a circular buffer that stores the sensor data. Therapycircuit 234 delivers one or more therapies to body 102. In oneembodiment, therapy 234 delivers one or more of an anti-bradycardiapacing therapy, an anti-tachycardia pacing therapy, a defibrillationtherapy, a cardiac resynchronization therapy, and a neurostimulationtherapy. In various embodiments, therapy circuit 234 includes one ormore of a pacing circuit to deliver pacing pulses, a defibrillationcircuit to deliver cardioversion/defibrillation pulses, aneurostimulation circuit to deliver neurostimulation, a drug deliverydevice to deliver one or more drugs, and a biologic therapy device todeliver one or more biologic therapies such as cell therapies and genetherapies. Implant control circuit 236 controls the operation ofimplantable medical device 210. Implant telemetry circuit 240 receivesdata from, and transmits data to, external system 225 via telemetry link115. In one embodiment, implantable medical device 210 includes ahermetically sealed housing containing at least sensor processingcircuit 232, therapy circuit 234, implant control circuit 236, implantmemory circuit 238, and implant telemetry circuit 240. In variousembodiments, sensor(s) 230 are each within the hermetically sealedhousing or external to the hermetically sealed housing butcommunicatively coupled to sensor processing circuit 232 via a wired orwireless communication link.

External system 225 represents an embodiment of external system 125 andincludes a user interface 242, an external control circuit 244, anexternal telemetry circuit 246, and one or more external memory circuits248. These components are each included in one or both of externaldevice 120 and remote device 124. User interface 242 allows a user suchas a physician or other caregiver to control hospitalization managementsystem 100 and include a user input device 250 and a presentation device252. User input device 250 receives commands and parameters from theuser. Presentation device 252 includes a printer and/or a display screento present to the user various information including informationindicative of operation of hospitalization management system 100 andinformation acquired and/or stored in various portions ofhospitalization management system 100. External control circuit 244controls the operation of external system 225. External telemetrycircuit 246 receives data from, and transmits data to, implantablemedical device 210 via telemetry link 115. External memory circuit(s)248 store data including external data representative of patientinformation. In one embodiment, the external data include data used inmanagement of heart failure patients and data transmitted from one ormore implantable or external medical devices (other than implantablemedical device 210) as well as data received by user input device 250.Examples of such external data include therapy parameters such as drugdosage and pacing parameters, diagnostic test results such as laboratorytest results and medical examination results, medical historyinformation such as patient demographics and history of cardiacconditions including heart failure symptoms and recovery information.

In one embodiment, implant control circuit 236 includes heart failureanalyzer 160. In another embodiment, external control circuit 244includes heart failure analyzer 160. In another embodiment, implantcontrol circuit 236 and external control circuit 244 each includeportions of heart failure analyzer 160. Heart failure analyzer 160receives a mode-change command and controls the operation of implantablemedical device 210 and/or external system 225 according to anoperational mode selected according to the mode-change command. In oneembodiment, the operational mode is selected from a hospitalizationmode, a post-hospitalization mode, and a non-hospitalization mode. Theseoperational modes each correspond to a heart failure managementalgorithm applied to a patient depending on the hospitalization statusof that patient.

FIG. 3 is a block diagram illustrating an embodiment of a heart failureanalyzer 360, which represents an embodiment of heart failure analyzer160. Heart failure analyzer 360 includes a data input 362, a mode switch364, a diagnostic data processor 366, a heart failure management module368, and a memory circuit 370.

Data input 362 receives diagnostic data indicative of one or moreconditions associated with heart failure. In the illustrated embodiment,data input 362 includes a sensor data input 372 and an external datainput 374. In other embodiments, data input 362 includes one or more ofsensor data input 372 and external data input 374, depending on the needof the heart failure management algorithms executed by heart failureanalyzer 360. Sensor data input 372 receives sensor data representativeof one or more physiological signals sensed by sensor(s) 230 ofimplantable medical device 210. External data input 374 receives theexternal data representative of patient information from external system225.

Diagnostic data processor 366 produces one or more parameters indicativeof one or more conditions associated with heart failure using thediagnostic data received by data input 362. Examples of such one or moreparameters include amplitude of third heart sounds (S3) produced usingthe heart sound signal, thoracic fluid volume produced using thethoracic impedance signal, respiration rate produced using the thoracicimpedance signal, heart rate and heart rate variability produced usingthe one or more electrograms, and parameters indicative of variousphysiological responses to patient's physical activities. In oneembodiment, diagnostic data processor 366 produces a parameter as afunction of a plurality of sensed physiological signals and patientinformation represented by selected sensor data and external datareceived by data input 362. In one embodiment, diagnostic data processor366 produces a trend using at least one of the one or more parameters.The trend is indicative of progression of heart failure, including anacute worsening of heart failure. An example of such a trend isillustrated in FIG. 4, which is further discussed below. In oneembodiment, diagnostic data processor 366 produces a trend of theparameter as the function of the plurality of sensed physiologicalsignals and patient information. In one embodiment, the one or moreparameters produced by diagnostic data processor 366, including thetrend, is presented using presentation device 252.

Mode switch 364 switches the operational mode of heart failure analyzer360 to one of a hospitalization mode, a post-hospitalization mode, and anon-hospitalization mode in response to a mode-change command. In theillustrated embodiment, mode switch 364 includes a mode selector 376 anda command receiver 378. In other embodiments, mode switch 364 includesany one or more of mode selector 376 and command receiver 378, dependingon how heart failure analyzer 160 determines the hospitalization statusof the patient. Mode selector 376 produces the mode-change commandautomatically using the one or more parameters produced by diagnosticdata processor 366. Command receiver 378 receives the mode-changecommand from external system 225. In one embodiment, the mode-changecommand is entered by the user through user input device 250.

Heart failure management module 368 executes a heart failure managementalgorithm selected from one or more stored heart failure managementalgorithms according to the operational mode. Memory circuit 370 storesthe one or more heart failure management algorithms, including at leasta hospitalization algorithm that is to be executed while the patient ishospitalized. In one embodiment, memory circuit 370 stores apost-hospitalization algorithm in addition to the hospitalizationalgorithm. The post-hospitalization algorithm is to be executed during apost-hospitalization period after the discharge of the patient from thehospital. In another embodiment, memory circuit 370 stores a baselinealgorithm in addition to the hospitalization algorithm and thepost-hospitalization algorithm. The baseline algorithm is to be executedafter the post-hospitalization period and before the patient ishospitalized.

FIG. 4 is a graph illustrating an example of a parameter 400 indicativeof progression of heart failure, including the acute worsening of heartfailure. Parameter 400 is for illustrative purpose only and representsthe one or more parameters produced by diagnostic data processor 366. Asillustrated, the amplitude of parameter 400 indicates the degree ofseverity of heart failure in a patient. In the illustrated embodiment,the one or more heart failure management algorithms stored in memorycircuit 370 include the baseline algorithm, the hospitalizationalgorithm, and the post-hospitalization algorithm.

During the non-hospitalization mode, parameter 400 indicates a degree ofseverity of heart failure that does not require hospitalization. Whenparameter 400 indicates that the patient is clinically stable (withoutsymptoms indicating a substantially degree of decompensation for 30days, for example), heart failure management module 368 establishes abaseline value 406 for parameter 400, using the one or more parametersproduced using data acquired during the clinically stable period, byexecuting the baseline algorithm during the non-hospitalization mode. Inone embodiment, data input 362 receives data selected according to therequirement of the baseline algorithm, and diagnostic data processor 366produces parameter 400 using the selected data. In one embodiment,selected one or more physiological signals represented by the receiveddata are smoothed with filters such as finite impulse response, infiniteimpulse response, and/or nonlinear filters. In another embodiment,regression analysis or curve fitting are used to estimate baseline value406.

At 402, mode switch 364 switches the operational mode of heart failureanalyzer 360 to the hospitalization mode from the non-hospitalizationmode when parameter 400 exceeds a hospitalization threshold value, orwhen a user command is received following the patient's admission into ahospital. During the hospitalization mode, heart failure managementmodule 368 analyzes therapy efficacy, produces therapy adjustmentsignals when necessary, and assesses risk of rehospitalization usingparameter 400 by executing the hospitalization algorithm. In oneembodiment, the therapy efficacy is analyzed by comparing parameter 400to its expected value 410 that is determined according to one or moretherapies applied to the patient. In various embodiments, the therapyadjustment signals are presented to the physician or other caregiverand/or result in automatic adjustment of therapy delivery. In oneembodiment, data input 362 receives data selected according to therequirement of the hospitalization algorithm, and diagnostic dataprocessor 366 produces parameter 400 using the selected data.

At 404, mode switch 364 switches the operational mode of heart failureanalyzer 360 to the post-hospitalization mode from the hospitalizationmode when parameter 400 decreases below a discharge threshold value, orwhen a user command is received after a decision to discharge thepatient from the hospital is made. Readiness to discharge is determinedby comparing one or more features extracted from parameter 400 duringthe hospitalization mode to corresponding one or more criteriastatistically established using a patient population. Examples of suchfeatures include change of value of parameter 400 from baseline value406, change of value of parameter 400 from its peak value prior to thehospitalization, a derivative of parameter 400, a frequency-domainfeature of parameter 400, and a measure of variance of parameter 400. Inone embodiment, as illustrated in FIG. 4, the readiness to discharge isindicated when parameter 400 does not exceed baseline value 406 by apredetermined margin b. During the post-hospitalization mode, heartfailure management module 368 monitors cardiac conditions and determinesa need for intervention including rehospitalization using parameter 400by executing the post-hospitalization algorithm. The need forintervention including rehospitalization is determined by comparing oneor more features extracted from parameter 400 during thepost-hospitalization mode to corresponding one or more criteriastatistically established using the patient population. Examples of suchfeatures also include change of value of parameter 400 from baselinevalue 406, change of value of parameter 400 from its peak value prior tothe hospitalization, a derivative of parameter 400, a frequency-domainfeature of parameter 400, and a measure of variance of parameter 400. Inone embodiment, the need for rehospitalization is indicated whenparameter 400 exceeds baseline value 406 by a predetermined margin 6, orwhen a positive slope of parameter exceeds a predetermined threshold,during the post-hospitalization mode. In one embodiment, thepredetermined margin or threshold for rehospitalization is lower thanthat of hospitalization but higher than that required to transition fromthe hospitalization mode to the post-hospitalization mode. In oneembodiment, data input 362 receives data selected according to therequirement of the post-hospitalization algorithm, and diagnostic dataprocessor 366 produces parameter 400 using the selected data.

FIG. 5 is a block diagram illustrating an embodiment of a heart failuremanagement module 568, which represents an embodiment of heart failuremanagement module 368. In the illustrated embodiment, heart failuremanagement module 568 includes a baseline analyzer 580, ahospitalization alarm generator 582, a therapy monitor 584, a riskanalyzer 586, a discharge planning analyzer 588, a post-hospitalizationmonitor 590, a rehospitalization alarm generator 592, and apost-hospitalization timer 594.

Baseline analyzer 580 is activated during the non-hospitalization modeand produces one or more baseline values of the one or more parametersproduced by diagnostic data processor 366 when the patient is clinicallystable. Heart failure is generally characterized by clinically stableperiods punctuated by episodes of decompensation and hospitalization.The one or more baseline values of the one or more parameters areproduced using the sensor data acquired when decompensation has not beendetected for a specified period of time, such as 30 days.

Hospitalization alarm generator 582 produces a hospitalization alarmsignal when the one or more parameters indicate a need forhospitalization during the non-hospitalization mode. In variousembodiments, the hospitalization alarm signal is produced as a toneaudible to the patient and/or transmitted to external system 225 fornotifying the patient and/or the physician or other caregiver usingpresentation device 252. In one embodiment, hospitalization alarmgenerator 582 produces the hospitalization alarm signal by comparing atleast one of the one or more parameters to a correspondinghospitalization threshold value. In another embodiment, hospitalizationalarm generator 582 produces the hospitalization alarm signal bycomparing a time derivative (slope) of at least one of the one or moreparameters to a corresponding hospitalization threshold derivativevalue. In one embodiment, mode switch 364 switches the operational modeof heart failure analyzer 360 from the non-hospitalization mode to thehospitalization mode in response to the hospitalization alarm signal.

Therapy monitor 584 is activated during the hospitalization mode andanalyzes efficacy of therapy using one or more parameters produced bydiagnostic data processor 366 and one or more corresponding expectedvalues of the one or more parameters associated with the one or moretherapies applied. The one or more therapies are adjusted if the one ormore parameters substantially deviate from the one or more expectedvalues.

Risk analyzer 586 is activated during the hospitalization mode andproduces a risk class parameter. The risk class parameter classifies alevel of risk for rehospitalization. In one embodiment, the level ofrisk for rehospitalization is a probability of rehospitalization withina specified period of time, and risk analyzer 586 calculates thisprobability using an empirically established mathematical formula usingthe one or more parameters produced by diagnostic data processor 366. Inone embodiment, risk analyzer 586 produces the class parameter bycomparing at least a risk parameter selected from the one or moreparameters produced by diagnostic data processor 366 to one or more riskthreshold values associated with the risk parameter. In one embodiment,the risk threshold value is a function of the baseline value of the riskparameter. In another embodiment, risk analyzer 586 produces the riskclass parameter by comparing a time derivative (slope) of at least oneof the one or more parameters to one or more risk threshold derivativevalues associated with the risk parameter.

Discharge planning analyzer 588 produces a discharge recommendationsignal using the risk class parameter during the hospitalization mode.In one embodiment, discharge planning analyzer 588 produces thedischarge recommendation signal when the risk class parameter fallsbelow a predetermined or programmed threshold. In one embodiment, modeswitch 364 switches the operational mode of heart failure analyzer 360from the hospitalization mode to the post hospitalization mode inresponse to the discharge recommendation signal.

Post-hospitalization monitor 590 is activated during thepost-hospitalization mode. Post-hospitalization monitor 590 monitors theone or more parameters produced by diagnostic data processor 366 andproduces signals indicative of need for medical intervention using theone or more parameters and predetermined and/or programmed criteriaassociated with the one or more parameters. The intervention may includeadjustments of one or more factors affecting conditions associated withheart failure, such as therapy, diet, and daily activities. Theadjustments of therapy include, for example, starting a therapy,stopping a therapy, and adjustment of therapy parameters such as drugdosage and pacing parameters. In one embodiment, the patient ismonitored more closely in the post-hospitalization mode than in thenon-hospitalization mode because the known elevated risk ofhospitalization during the period of time (such as 180 days) followingthe hospitalization. This requires, for example, monitoring of moreparameters representing physiological signals sensed by more sensors andanalysis of more features extracted from the one or more parameters.

Rehospitalization alarm generator 592 produces a rehospitalization alarmsignal when the one or more parameters produced by diagnostic dataprocessor 366 indicate a need for rehospitalization during thepost-hospitalization mode. In one embodiment, rehospitalization alarmgenerator 592 produces the rehospitalization alarm signal by comparingat least one of the one or more parameters to a correspondingrehospitalization threshold value. In another embodiment,rehospitalization alarm generator 592 produces the rehospitalizationalarm signal by comparing a time derivative of at least one of the oneor more parameters to a corresponding rehospitalization thresholdderivative value. In one embodiment, mode switch 364 switches theoperational mode of heart failure analyzer 360 from thepost-hospitalization mode to the hospitalization mode in response to therehospitalization alarm signal.

Post-hospitalization tinier 594 times a post-hospitalization period thatstarts with the post-hospitalization mode. In one embodiment, thepost-hospitalization period is a predetermined period. In anotherembodiment, the post-hospitalization period is programmable, such asusing user input device 250. In one embodiment, mode switch 364 switchesthe operational mode of heart failure analyzer 360 from thepost-hospitalization mode to the non-hospitalization mode in response tothe expiration of the post-hospitalization period.

FIG. 6 is a flow chart illustrating a method 600 for managinghospitalization of a heart failure patient using a hospitalizationmanagement system such as hospitalization management system 100. In theillustrated embodiment, the hospitalization management system has aplurality of operational modes including a non-hospitalization mode, ahospitalization mode, and a post-hospitalization mode, and method 600 isapplied to operate this hospitalization management system.

At 610, the hospitalization management system enters thenon-hospitalization mode. In one embodiment, the hospitalizationmanagement system enters each of its operational modes in response to amode-change command received from a user. In another embodiment, thehospitalization management system enters each of its operational modesin response to a mode-change command produced automatically usingpatient information including at least a physiological signal sensedfrom the patient. The hospitalization management system selects a heartfailure management algorithm upon entering each of its operational modesand executes that algorithm during the operational mode. During thenon-hospitalization mode, the hospitalization management system executesa baseline algorithm.

At 612, diagnostic data indicative of one or more conditions associatedwith heart failure are received. The diagnostic data include sensor datarepresentative of one or more physiological signals sensed by one ormore implantable sensors being part of or communicatively coupled to animplantable medical device of the hospitalization management system. Inone embodiment, diagnostic data further include external datarepresentative of patient information stored an external systemcommunicatively coupled to the implantable medical device. In oneembodiment, the diagnostic data received during each operational modeinclude input data required to execute the heart failure managementalgorithm selected for that operational mode.

At 614, one or more parameters are produced using the diagnostic data.In one embodiment, the selected heart failure management algorithmdetermines which one or more parameters are produced during eachoperational mode.

At 616, one or more baseline values for the one or more parameters areestablished. In one embodiment, a baseline value for each of the one ormore parameters is produced using baseline data including sensor datarepresentative of the one or more sensor signals sensed by the one ormore implantable sensors within a clinically stable period (whendecompensation is not detected) during the non-hospitalization mode.

At 618, whether the patient needs hospitalization is determined. In oneembodiment, whether the patient needs hospitalization is determined bycomparing at least one of the one or more parameters to a correspondinghospitalization threshold value. In another embodiment, whether thepatient needs hospitalization is determined by comparing a timederivative (slope) of at least one of the one or more parameters to acorresponding hospitalization threshold derivative value. In oneembodiment, in response to each determination that the patient needshospitalization, a hospitalization alarm signal is produced.

At 630, the hospitalization management system enters to hospitalizationmode after the determination that the patient needs hospitalization ismade at 618. If the patient does not need hospitalization as determinedat 618, the hospitalization management system remains in thenon-hospitalization mode. In one embodiment, the operational mode isswitched from the non-hospitalization mode to the hospitalization modein response to the determination that the patient needs hospitalization(such as in response to the hospitalization alarm signal). In anotherembodiment, the operational mode is switched from thenon-hospitalization mode to the hospitalization mode in response to themode-change command entered by a physician or other caregiver upon thepatient's admission into a hospital. During the hospitalization mode,the hospitalization management system executes a hospitalizationalgorithm.

At 632, the diagnostic data are received according to the requirementfor executing the hospitalization algorithm. At 634, the one or moreparameters are produced using the diagnostic data according to thehospitalization algorithm. In various embodiments, the diagnostic datareceived and the one or more parameters produced during differentoperational modes may be substantially identical or substantiallydifferent, depending on the need for patient monitoring and availabilityof types of data. In one embodiment, a trend indicative of progressionof heart failure is produced using at least one of the one or moreparameters. The trend indicates acute worsening of heart failure. In oneembodiment, the trend is presented to the physician or other caregiverusing a display screen and/or a printer. In one embodiment, the trend isthe trend of a parameter being a function of the sensor data and theexternal data.

At 636, therapy efficacy is monitored, and therapy is adjusted whenneeded in response to the outcome of the monitoring. The efficacy oftherapy administrated during the hospitalization mode is analyzed bycomparing the one or more parameters to the corresponding expectedvalues of the one or more parameters. The expected values represent thepredicted response of the patient to the therapy. In one embodiment, thetherapy delivered includes one or more of an anti-bradycardia pacingtherapy, an anti-tachycardia pacing therapy, a defibrillation therapy, acardiac resynchronization therapy, and a neurostimulation therapy.

At 638, a risk class parameter is produced. The risk class parameterclassifies a level of risk for rehospitalization. In one embodiment, therisk class parameter represents the probability of rehospitalizationwithin a specified period. In one embodiment, the risk class parameteris produced by comparing at least one of the one or more parameters toone or more risk threshold values associated with the risk parameter. Inanother embodiment, the risk class parameter is produced by comparing atime derivative (slope) of at least a risk parameter of the one or moreparameters with one or more risk threshold derivative values associatedwith the risk parameter.

At 640, whether the patient is ready to be discharged from the hospitalis determined using the risk class parameter. In one embodiment, inresponse to a determination that the patient is ready to be discharged,a discharge recommendation signal is produced and presented to thephysician or other caregiver.

At 650, the hospitalization management system enters apost-hospitalization mode after the determination that the patient isready to be discharged at 640. If the patient is not ready to bedischarged as determined at 640, the hospitalization management systemremains in the hospitalization mode. In one embodiment, the operationalmode is switched from the hospitalization mode to the posthospitalization mode in response to the determination that the patientis ready to be discharged (such as in response to the dischargerecommendation signal). In another embodiment, the operational mode isswitched from the non-hospitalization mode to the hospitalization modein response to the mode-change command entered by the physician or othercaregiver before the patient leaves the hospital. During thepost-hospitalization mode, the hospitalization management systemexecutes a post-hospitalization algorithm.

At 652, the diagnostic data are received according to the requirementfor executing the post-hospitalization algorithm. At 654, the one ormore parameters are produced using the diagnostic data according to thepost-hospitalization algorithm.

At 656, the one or more parameters are monitored, and a need forintervention is signaled, when needed, in response to the outcome of themonitoring. Signals indicative of need for intervention are producedduring the post-hospitalization mode when the one or more parametersindicate such need according to predetermined and/or programmedcriteria. Examples of such intervention include adjustments of one ormore factors affecting conditions associated with heart failure, such astherapy parameters, diet, and daily activities.

At 658, whether the patient needs rehospitalization is determined. Inone embodiment, whether the patient needs rehospitalization isdetermined by comparing at least one of the one or more parameters to acorresponding rehospitalization threshold value. In another embodiment,whether the patient needs rehospitalization is determined by comparing atime derivative of at least one of the one or more parameters to acorresponding rehospitalization threshold derivative value. In oneembodiment, a rehospitalization alarm signal is produced when the one ormore parameters indicate a need for rehospitalization.

In response to a determination that the patients needs rehospitalizationat 658, the patient is to be rehospitalized, and the operational mode ofthe hospitalization management system reenters the hospitalization modeat 630. In one embodiment, the operational mode is switched from thepost-hospitalization mode to the hospitalization mode in response to therehospitalization alarm signal. In another embodiment, the operationalmode is switched from the non-hospitalization mode to thehospitalization mode in response to the mode-change command entered bythe physician or other caregiver upon the patient's readmission into thehospital.

A post-hospitalization period is started when the hospitalizationmanagement system enters the post-hospitalization mode and is timedduring the post-hospitalization mode. At 660, if thepost-hospitalization period has expired, the operational mode isswitched from the post-hospitalization mode to the non-hospitalizationmode.

It is to be understood that the above detailed description is intendedto be illustrative, and not restrictive. Other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A system for managing a heart failure patient,the system comprising: a sensor processing circuit configured to receiveone or more physiological signals and produce sensor data representativeof the one or more physiological signals; and a heart failure analyzercircuit coupled to the sensor processing circuit, the heart failureanalyzer configured to operate in a post-hospitalization mode includingto: receive diagnostic data including information about the sensor data,the diagnostic data indicative of one or more conditions associated withheart failure decompensation, wherein the diagnostic data includespost-hospitalization respiration data associated with the patient; andproduce a risk class parameter classifying a level of risk forrehospitalization within a specified period using the diagnostic data.2. The system of claim 1, wherein the sensor processing circuit isconfigured to include or to be coupled to an impedance sensor configuredto sense a thoracic impedance, and wherein the sensor processing circuitis configured to determine the respiration data using information aboutthe thoracic impedance.
 3. The system of claim 2, wherein the sensorprocessing circuit is configured to determine the respiration dataincluding a respiration characteristic comprising a respiration rate. 4.The system of claim 1, wherein the heart failure analyzer is configuredto operate in the post-hospitalization discharge mode upon beingtriggered by heart failure analyzer circuit determining that the sensordata has met at least one specified criterion.
 5. The system of claim 1,wherein the heart failure analyzer is configured to operate in thepost-hospitalization discharge mode upon being triggered by a usercommand being received after a decision to discharge the patient from ahospitalization.
 6. The system of claim 1, wherein the heart failureanalyzer circuit includes at least one specified re-hospitalizationcriterion and at least one specified hospitalization criterion, whereinthe at least one specified re-hospitalization criterion is easier tomeet than the at least one specified hospitalization criterion.
 7. Thesystem of claim 1, wherein the heart failure analyzer is configured toinclude respiration data obtained outside of the post-hospitalizationmode in the diagnostic data used to produce the risk class parameterclassifying the level of risk for rehospitalization.
 8. The system ofclaim 7, wherein the heart failure analyzer is configured to includerespiration data obtained in a hospitalization mode in the diagnosticdata used to produce the risk class parameter classifying the level ofrisk for rehospitalization.
 9. The system of claim 8, wherein the heartfailure analyzer is configured to include respiration data obtained in anon-hospitalization mode in the diagnostic data used to produce the riskclass parameter classifying the level of risk for rehospitalization. 10.The system of claim 1, comprising an implantable medical deviceincluding the sensor processing circuit, and a remotely-accessibleexternal patient management system including or coupled to at least aportion of the heart failure analyzer circuit to permit a caregiver tomonitor the patient from a remote location.
 11. The system of claim 6,wherein the heart failure analyzer circuit is configured to receive thepatient's medical history information including patient demographics andhistory of cardiac and produce the one or more parameters indicative ofheart failure decompensation using the diagnostic data including thesensor data and the medical history information.
 12. A system formanaging a patient, the system comprising: a heart failure analyzercircuit configured to operate in a post-hospitalization mode includingto: receive diagnostic data including information about patientphysiological sensor data, the diagnostic data indicative of one or moreconditions associated with heart failure decompensation, wherein thediagnostic data includes post-hospitalization respiration dataassociated with the patient; and classify a level of risk forrehospitalization using the diagnostic data including using arespiration characteristic comprising a respiration rate.
 13. The systemof claim 12, wherein the heart failure analyzer is configured to operatein the post-hospitalization discharge mode: upon being triggered byheart failure analyzer circuit determining that the sensor data has metat least one specified criterion; and upon being triggered by a usercommand being received after a decision to discharge the patient from ahospitalization.
 14. The system of claim 12, wherein the heart failureanalyzer circuit includes at least one specified re-hospitalizationcriterion and at least one specified hospitalization criterion, whereinthe at least one specified re-hospitalization criterion is easier tomeet than the at least one specified hospitalization criterion.
 15. Thesystem of claim 12, wherein the heart failure analyzer is configured to:use respiration data obtained in a hospitalization mode in thediagnostic data used to classify the level of risk forrehospitalization; and use respiration data obtained in anon-hospitalization mode in the diagnostic data used to classify thelevel of risk for rehospitalization.
 16. The system of claim 12,comprising an implantable medical device including: a sensor processingcircuit configured to receive one or more physiological signals andproduce the sensor data as representative of the one or morephysiological signals; and a remotely-accessible external patientmanagement system including or coupled to at least a portion of theheart failure analyzer circuit to permit a caregiver to monitor thepatient from a remote location.
 17. The system of claim 12, wherein theheart failure analyzer circuit is configured to produce one or moreparameters indicative of heart failure decompensation using thediagnostic data, and produce a trend indicative of progression of heartfailure using at least one parameter of the one or more parameters. 18.The system of claim 17, further comprising a presentation deviceconfigured to present the trend.
 19. A system for managing a heartfailure patient, the system comprising an implantable medical devicecomprising: a sensor processing circuit configured to receive one ormore physiological signals and produce sensor data representative of theone or more physiological signals; and a heart failure analyzer circuitcoupled to the sensor processing circuit, the heart failure analyzerconfigured to operate in a post-hospitalization mode including to:receive diagnostic data including information about the sensor data, thediagnostic data indicative of one or more conditions associated withheart failure decompensation, wherein the diagnostic data includespost-hospitalization respiration data associated with the patient; andclassify a level of risk for rehospitalization within a specified periodusing the diagnostic data including respiration rate determined fromthoracic impedance.
 20. The system of claim 19, wherein the heartfailure analyzer circuit includes at least one specifiedre-hospitalization criterion and at least one specified hospitalizationcriterion, wherein the at least one specified re-hospitalizationcriterion is easier to meet than the at least one specifiedhospitalization criterion.